Range measurement systems have been used in a variety of applications, including speed measurement for vehicles for law enforcement purposes. In addition, speed control systems have been incorporated into automobiles for years to allow a driver to set the speed he wishes to travel. However, under many circumstances, constant speed is not a safe manner of travel. Safe drivers do not drive at a constant speed but rather keep a parameter referred to as "time to collision" relatively constant. In this manner, at lower speeds automobiles can travel closer together whereas at higher speeds more distance is required between automobiles to allow for safe stopping distance.
In order to apply active ranging systems to an automated driving system, a highly accurate but low cost ranging system must be combined with systems capable of controlling speed to allow for relative consistency in the time to collision parameter during operation of the vehicle. Accordingly, a need has arisen for systems and methods which combine ranging operations using simple low cost ranging systems with digital processing capability to allow for automatic control of the speed of vehicle incorporating the ranging system.